The eUSB2 interface is becoming increasingly common in designs with advance processors. In order to enable backwards compatibility with USB 2.0 hosts and devices, an eUSB2 repeater must be placed between the processor and the USB connector to convert 1.2V eUSB2 signaling to 3.3V USB 2.0 signaling. A common question from PCB layout engineers is where should the repeater be placed between the processor and connector?
Fortunately, the eUSB2 specification gives clear instructions on the maximum loss between the repeater and the processor, or SoC, as well as the loss between the repeater and the USB connector.
The max loss between the SoC and the repeater is -1.2dB, while the max loss between the USB connector and the repeater is 2.0dB. This translates to around 10 inches of loss between the repeater and SoC, which allows flexible placement in most designs. The trace distance on the USB-side of the repeater is even greater, around 16 inches; however, some factors can increase or decrease this distance, like board material or the number of vias in the signal path.
For more layout recommendations for eUSB2 repeaters, please read our eUSB2 Repeater Design Guide.